A sensor module having a configuration in FIG. 10 (for example, see Patent Document 1) is known as one that can measure a core body temperature Tb without being affected by an individual difference in heat resistance Rx of a subcutaneous tissue.
The following two equations hold in the sensor module.Tb=(Tt−Ta)Rx/R1+Tt  (1)Tb=(Tt′−Ta′)Rx/R2+Tt′  (2)
Where Ta and Ta′ are temperatures measured with temperature sensors on top surface sides of heat flux sensors on the left and right in FIG. 10, respectively. Tt and Tt′ are temperatures measured with temperature sensors on bottom surface sides of heat flux sensors on the left and right in FIG. 10, respectively. R1 and R2 are heat resistances of heat insulators of the heat flux sensors.
The following equation (3) can be obtained when the heat resistance Rx is eliminated by a combination of the equations (1), (2).
                    [                  Mathematical          ⁢                                          ⁢          Formula          ⁢                                          ⁢          1                ]                                                            Tb        =                                            R              ⁢                                                          ⁢              2              ⁢                              (                                  Tt                  -                  Ta                                )                            ⁢                              Tt                ′                                      -                          R              ⁢                                                          ⁢              1              ⁢                              (                                                      Tt                    ′                                    -                                      Ta                    ′                                                  )                            ⁢              Tt                                                          R              ⁢                                                          ⁢              2              ⁢                              (                                                      T                    ⁢                                                                                  ⁢                    t                                    -                                      T                    ⁢                                                                                  ⁢                    a                                                  )                                      -                          R              ⁢                                                          ⁢              1              ⁢                              (                                                      Tt                    ′                                    -                                      Ta                    ′                                                  )                                                                        (        3        )            
Accordingly, in the sensor module of FIG. 10, the core body temperature Tb can be calculated without being affected by the individual difference of the heat resistance Rx of the subcutaneous tissue.